This disclosure relates generally to wireless communication networks and, more particularly, to a system and method for route optimization in a wireless Internet Protocol (IP) network.
One common communication language, or protocol, used in communication networks is Transmission Control Protocol/Internet Protocol (TCP/IP). TCP/IP facilitates the transfer of information in various network types, including the Internet, intranets and extranets, and wireless networks.
TCP/IP is a two-layered program. The Transmission Control Protocol (TCP), which refers to the higher layer, manages the assembling of a message or file into smaller packets that are transmitted over a particular network and received by a TCP layer that reassembles the packets into the original message. The Internet Protocol (IP), which refers to the lower layer, handles the address part of each packet so that it gets to the proper destination. Each source on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, they are reassembled at the destination.
TCP/IP uses a client/server model of communication. For example, a computer user (a client) requests and is provided a specific Web page (a service) by another computer (a server) in the network. TCP/IP communication is primarily point-to-point, meaning each communication is from one point (or host computer) in the network to another point or host computer. TCP/IP and the higher-level applications that use it are collectively said to be xe2x80x9cconnectionlessxe2x80x9d because each client request is considered a new request unrelated to any previous one (unlike ordinary phone conversations that require a dedicated connection for the call duration). Being connectionless, network paths are free and can thus be used continuously. It is understood that the TCP layer itself is not connectionless as far as any one message is concerned. Its connection remains in place until all packets in a message have been received. It is further understood that the general characteristics of TCP/IP are well known to those of average skill in the art and thus will not be described further herein.
Certain TCP/IP networks allow the use of mobile nodes, such as a laptop computer equipped with a wireless Local Area Network (LAN) card. Such a network provides a user with the ability to access services using their mobile node while moving through the network. While accessing these services, however, packets may be lost, thus degrading the quality of the service and the network may not be utilized in an optimal fashion thereby causing various inefficiencies.
In order to address these problems, one prior art route optimization theory suggests sending packets (or datagrams) from a correspondent node (such as a personal computer) to a mobile node without going through a home agent (HA, such as a server). The prior art optimization theory assumes that all foreign networks contain foreign agents (FAs).
In certain situations, however, a foreign network may not contain a FA. For example, a foreign network may simply not have a configured FA or may lose the FA due to system failure. If the foreign network does not contain a FA, a collocated care-of-address (CCOA) is provided to mobile nodes, instead of a conventional care-of-address (COA). As a mobile node moves to a new foreign network, it obtains a new CCOA and then registers with the new foreign network. According to the prior art route optimization theory, however, a correspondent node will not be updated with the mobile node""s COA until after a predetermined period of time has expired. Specifically, the correspondent node""s binding cache entry for the mobile node in the old foreign network must expire before the correspondent node is updated with the new COA. Until that occurs, the correspondent node will continue to send data packets to the old COA which will cause loss of data and service degradation.
A technical advance is provided by a system and method for route optimization in a wireless Internet Protocol (IP) network. In one embodiment, the system sends a data packet to a home agent of the IP network and then transmits the data packet to a mobile node using a first address. A list of correspondent nodes associated with the mobile node is maintained so that one or more messages, such as a binding update message, can be sent. Thereafter, subsequent data packets can be transmitted directly to the mobile node using the first address.
In another embodiment, the system transmits a registration request, including a new address, to the home agent and transmits a registration reply in response to the registration request to the mobile node. The new address is then compared to an old address. If the new address and the old address are not equal, a binding update message is transmitted to the correspondent node and a binding acknowledgment message is transmitted to the home agent in response. Thereafter, all subsequent messages are transmitted to the mobile node via the new address.
In another embodiment, the system sends a de-registration request to the home agent when the mobile node returns to its home location. A binding update message is sent to a correspondent node so that the binding update message includes a lifetime value of zero. The mobile node""s entry at the prior location is then invalidated.
In another embodiment, the system maintains a list of correspondent nodes with which the mobile node is currently communicating. If the mobile node changes its address, a registration request is sent to the home agent with a correspondent node extension (CNE), the CNE including the list of correspondent nodes. A binding update is then sent by the home agent to each of the correspondent nodes on the list. Each of the correspondent nodes may then respond to the home agent with a binding acknowledgment message.
These embodiments, as well as others which will become apparent, are achieved in a system that includes a plurality mobile nodes and correspondent nodes that communicate with each other through various combinations of new and old foreign networks and foreign agents, discussed in greater detail below.